The present invention relates generally to the field of wastewater treatment systems. More particularly, the invention relates to techniques for decreasing total organic content of high strength wastewaters using a combination of anaerobic and aerobic treatment.
In the field of wastewater treatment, a number of different system types are known and are currently in use. In general, these may consist of primary treatment, secondary treatment, and, where desired, tertiary treatment. Primary treatment is often limited to screening and suspended solids removal. Secondary treatment may include a wide range of biological processes, such as biochemical oxygen demand (BOD) reduction, nitrification, de-nitrification, and so forth. Following secondary treatment, further settling, filtering, polishing and other operations may be performed before the wastewater is advanced to final discharge.
In a number of the processes used for wastewater treatment, particulate matter may be caused to precipitate from the wastewater and collect on the bottom of a vessel. Reactor vessels for secondary treatment, for example, may hold wastewater in a reactor vessel, along with biological support media. The biological support media includes bacteria that proliferate and serve to treat the water in the reactor vessel by circulation of the water over the support media. In addition to the biological support media, the reactor vessel may include aeration systems to promote the growth and sustenance of the microbial growth. For example, the aeration systems may bubble compressed air through the wastewater, feeding the bacteria and causing the media to move so as to adequately circulate the wastewater (and the substrate in the wastewater such as BOD) over the biological growth, thereby treating the wastewater. Therefore, the energy demands associated with the secondary treatment process generally increase the overall operational costs for wastewater treatment. Moreover, secondary treatment of the wastewater generates debris and sludge (waste biomass), which generally is removed by clarifier or a dissolved air flotation (DAF).